In manufacturing a semiconductor device or a flat panel display (FPD), various processes such as a film forming process, a heat treatment process, a dry etching process, a cleaning process and the like are performed in a vacuum vessel by using required processing gases. For example, apparatuses for performing such vacuum processes are disclosed in Japanese Patent Laid-open Publication Nos. 2000-127069 and H3-087386). In order to load and unload a target substrate, e.g., a semiconductor wafer or a glass substrate, without opening the vacuum vessel or vacuum processing chamber to the atmosphere, the apparatuses include a vacuum transfer chamber capable of maintaining a reduced pressure therein all the time or capable of being switched selectively between an atmospheric state and a depressurized state. The vacuum transfer chamber is connected to the vacuum processing chamber via a gate valve and a transfer robot is provided in the vacuum transfer chamber.
However, the vacuum processing apparatus has a problem of organic contamination that organic substances generated from a moving part or a frictional part in the vacuum transfer chamber are attached to the target object. Generally, the amount of organic contamination (absorption) of the target object in a vacuum state is much larger than that in the atmosphere. In particular, if the vacuum processing apparatus has a cluster tool type structure, an overall processing time, i.e. a stay time of the target object, takes long due to many processes in the system. Further, since processing under a high vacuum, e.g., 10−4 Pa, tends to increase along with the trend of high precision of processes, there is a case where the vacuum transfer chamber is maintained at a vacuum pressure, e.g., 10 mTorr (about 1.33 Pa) or less. As the vacuum transfer chamber is evacuated to a high vacuum level, organic substances are easily attached to the target object.
Such organic attachment or contamination deteriorates the reliability of processes such as film forming and etching processes in the vacuum processing chamber, resulting in a poor production yield. For example, in case of forming a gate oxide film, an oxide film withstand voltage is degraded, and native oxide film growth is accelerated to increase a contact resistance in forming a contact. Furthermore, incubation time increases in the film forming process, which leads to increase of variation in thickness.
Particularly, if organic substances which are produced or scattered from grease applied to a vacuum sealing O-ring or bearing, which are generated from a transfer mechanism, e.g., a transfer belt, or which are detached from surfaces of components in the processing chamber after being attached thereto due to poor cleaning, are attached to the surface of the target object, it is hard to remove the organic substances and a defective area on a target surface becomes larger. Therefore, the production yield is significantly reduced as described above.